This invention relates to a system and a method for driving a nematic liquid crystal.
When two transparent flat plates having transparent electrodes and sandwiching a nematic liquid crystal are placed between two polarizing plates, transmittance of light passing through the polarizing plates changes with voltages applied to the transparent electrodes.
Since liquid crystal display devices based on the above principle can be shaped flat and are operative with low electric power, they have been widely used in wrist watches, electronic calculating machines, and so forth.
In recent years, they are also used in combination with color filters to form color display devices in note-type personal computers and small liquid crystal TV sets, for example. In such liquid crystal displays, dots of three colors, red, green and blue, are selectively combined to display desired colors. However, color filters are very expensive and need a high accuracy when bonded to panels. Moreover, they need a triple number of dots to ensure an equivalent resolution as compared with black-and-white liquid crystal display panels. Therefore, liquid crystal color panels require a triple number of drive circuits typically in the horizontal direction. This means an increase of the cost of drive circuits themselves and the cost for increased manhours for connecting drive circuits to the panel at a triple number of points.
That is, the use of color filters with liquid crystal panels to display color images involves many disadvantageous factors from the viewpoint of expense.
To avoid the problems caused by the use of color filters, color liquid crystal display devices as disclosed in Japanese Patent Laid-Open 1-179914 (1989) have been proposed to display color images by combining a black-and-white panel and three-color back-lighting in lieu of color filters. Certainly, this method seems more likely to realize high-fidelity color images economically. Actually, however, because of the difficulty in driving liquid crystals at a high speed with conventional drive techniques, no such device has been brought into practice.
Another problem with conventional liquid crystal display devices was slow responses of liquid crystals. Due to this, liquid crystal display devices have been inferior to CRT displays especially when used as TV displays for displaying moving images or as personal computer displays required to follow quick movements of a mouse cursor.